This application claims priority to Japanese Patent Application 2001-217181 filed on Jul. 17, 2001, the disclosure of which is incorporated herein by reference in its entirety.
The invention relates to a bending method for bending a work of a plate shape by moving a die, with the work being butted against a butting member. The invention also relates to a bending apparatus, such as a press brake, for conducting such bending.
A typical press brake is, as shown in FIGS. 5 and 6, composed of a press machine main unit 1 and a back gauge mechanism 2 arranged behind the press machine main unit 1. In the press machine main unit 1, a ram 5 holding an upper die 3 and a table 6 holding a lower die 4 are positioned so as to vertically oppose to each other. The ram 5 is moved upward and downward by a reciprocating mechanism driven by a hydraulic cylinder or a servomotor. A work W is bent to a predetermined angle when the reciprocating mechanism is driven to lower the upper die 3 for pushing the work W by a predetermined amount into a V-shaped groove of the lower die 4.
The back gauge mechanism 2 has a pair of butting members 9 and 10 against which the rear end edge of the work W is butted. The members 9 and 10 are arranged side by side. Each of the butting members 9 and 10 are moveable forward and backward (indicated as an xe2x80x9cAxe2x80x9d direction in FIG. 6), side to side (indicated as an xe2x80x9cExe2x80x9d direction in FIG. 6), and upward and downward (indicated as a xe2x80x9cCxe2x80x9d direction in FIG. 5). In FIG. 6 a slide guide 11 supports the butting members 9 and 10 such that the butting members are able to slide in the sideways directions E in a reciprocating manner. Both the end portions of the slide guide 11 are connected to drive mechanisms 12 and 13, such as ball screw mechanisms, respectively. Prior to bending work, the right and left drive mechanisms 12 and 13 are driven to define the positions of the butting members 9 and 10 in the forward and backward directions, or the A direction. The work W is sent to be positioned between the upper die 3 and the lower die 4 of the press machine main unit 1, and is butted against each of the butting members 9 and 10 at the rear end edge thereof. A predetermined bending dimension is obtained when the work W is bent while the work is being butted in this way.
FIGS. 7 and 8 show a state when the work W of a plate shape, i.e., having a plate shape, is bent. In FIG. 7, a distance B1 between a rear end edge 15 and a bending position 16 of the work W is generally referred to as an xe2x80x9cabsolute dimension of bending.xe2x80x9d Further, in FIG. 8, a distance L between the rear end edge 15 of the bent work W and an intersection point Po at which planes passing through the outer faces of the work W cross is referred to as an xe2x80x9couter bending dimension.xe2x80x9d Also, a distance B2 between the rear end edge 15 of the bent work W and an intersection point Pi at which planes passing through the inner faces of the work W cross is referred to as an xe2x80x9cinner bending dimension.xe2x80x9d The outer dimension L and the inner dimension B2 with a bending angle of 90xc2x0 are shown in FIG. 9.
The outer dimension L is generally larger than the absolute dimension B1, and the difference between the two is referred to as an xe2x80x9celongation amount.xe2x80x9d This xe2x80x9celongation amountxe2x80x9d of an outer dimension is dependent on bending conditions including a bending angle and a thickness of the work W. A xe2x80x9cbending dimensionxe2x80x9d generally means the outer dimension L. This is because drawings for sheet-metal working often carry the outer dimension L, and further, the outer dimension L is the most easily measurable dimension in the measurement of the work W with a measuring device such as a vernier caliper after completing bending. Accordingly, as used herein, the xe2x80x9cbending dimensionxe2x80x9d means the outer dimension L.
Generally, prior to bending, the material and the thickness of the work W, conditions of bending such as dies, a target value of a bending dimension, and a target value of a bending angle are given. A bending dimension can be determined by calculating an elongation amount from the bending conditions and the target value of a bending angle, obtaining the absolute dimension B1 by the subtraction of the elongation amount from the target value of a bending dimension, and then, as shown in FIG. 10, setting a distance S, measured between a blade tip 3a of the upper die 3 and the butting members 9 and 10 of the back gauge mechanism 2, equal to the absolute dimension B1. Further, a bending angle can be determined, as shown in FIG. 11, by a push-in amount of the work W into a groove 4a of the lower die 4. The push-in amount is in other words a movement distance d (hereinafter referred to as an xe2x80x9coperation amountxe2x80x9d) measured between a contact position Y1 where the upper die 3 contacts with the work W and an endmost position Y2 of the downward movement of the upper die 3. This operation amount is computed in advance from the given bending conditions and the target value of a bending angle.
Whether or not a target bending dimension and a target bending angle are achievable when bending the work W of a plate shape with the press brake having the arrangement described above is confirmed by trial bending of the work W.
First, an elongation amount in bending is computed, and then the butting members 9 and 10 of the back gauge mechanism 2 are positioned based on the computed value and the target value of a bending dimension. Next, the operation amount d of the upper die 3 is computed, and the work W positioned by the back gauge mechanism 2 is bent when the upper die 3 is moved according to the computed value of the operation amount d.
After the trial bending described above, the work W is taken out, and a bending angle is measured with a device such as a protractor. When the measured value of the bending angle agrees with a target value, the bending dimension is also measured with a device such as a vernier caliper. If the measured value of the bending angle does not agree with the target value, the bending dimension is not measured. This is because an elongation amount is dependent on a bending angle, and therefore, as long as a measured value of a bending angle does not agree with a target value of the bending angle, there is no way to know the difference between a target value of a bending dimension and a measured value of the bending dimension through the measurement of a bending dimension.
When the measured value of a bending angle does not agree with the target value, an operation amount of the upper die 3 is corrected according to an amount of the error. After the correction, trial bending may be again conducted to confirm that a measured value of a bending angle agrees with the target value.
When a measured value of a bending angle agrees with the target value, a bending dimension is measured with a device such as a vernier caliper. Here, positions of the butting members 9 and 10 are corrected when the measured value does not agree with the target value. After the correction, trial bending may be again conducted to confirm that the measure value of a bending dimension agrees with the target value.
Generally, a target bending angle and a target bending dimension are not obtainable when bending is made only based on an elongation amount and an operation amount obtained by computation. Therefore, according to the method of adjustment described above, the press machine main unit 1 is first adjusted to obtain a target bending angle, and then the back gauge mechanism 2 is adjusted to obtain a target bending dimension. This requires at least one time of trial bending for adjustment to obtain a target bending angle, and also requires at least one time of trial bending for adjustment to obtain a target bending dimension. Thus, at least two times in total of trial bending must be conducted in this case.
The invention was made to solve such problems described above, and it is an object of the invention to provide a bending method and bending apparatus with which a target bending angle and bending dimension are obtainable by performing trial bending only one time.
In accordance with one embodiment, the invention provides a method for bending work having a plate shape by moving a die toward the work, the work butted against a butting member. The method comprises computing an initial operation amount of the die from a target bending angle; positioning the butting member according to a target bending dimension; performing a trial bending step for bending a work by moving the die according to the initial operation amount with the work being butted against the positioned butting member; measuring a measured bending angle and a measured bending dimension of the work bent in the trial bending step; and determining that the measured bending angle of the work disagrees with the target bending angle. The method further includes computing a correction value for the initial operation amount of the die to provide a corrected operation amount; computing an estimated bending dimension of the work; correcting a position of the butting member according to the estimated bending dimension such that the butting member is disposed in a corrected position; and bending a second work by moving the die the corrected operation amount, the second work being butted against the butting member disposed in the corrected position.
In accordance with a further embodiment, the invention provides a bending apparatus for bending work comprising a butting portion having a butting member against which a work of a plate shape is butted; a die for bending the work butted against the back gauge mechanism; a reciprocating mechanism for reciprocating the die in a direction toward a plate face of the work; a data input portion for inputting data regarding bending conditions including a target bending angle and a target bending dimension of the work to be processed, and for inputting a measured bending angle and a measured bending dimension of the work obtained by trial bending of the work; and a first computation portion for conducting an initial computation to compute an initial operation amount of the die based on the target bending angle. The bending apparatus further includes a second computation portion for conducting a correction computation and an estimate computation when the respective measured bending angle and the measured bending dimension are inputted through the data input means; the correction computation generating a correction value for the initial operation amount of the die to provide a corrected operation amount; and the estimate computation being for computing an estimated bending dimension of the work. Additionally, the apparatus includes a control portion controlling a drive of the reciprocating mechanism based on the initial operation amount of the die and, after trial bending, the corrected operation amount, the control portion further controlling a drive of the butting portion according to the target bending dimension and, after trial bending, the estimated bending dimension.